Movie 1: after episode 55
Movie 2: after episode 96
Movie 3: after episode 132
Movie 4: after episode 167
Movie 5(about to come out this fall garanteed: Final Confrontation):
after (around) episode 200-300
All anime movies have nothing to do with the storyline of the series they go to. They're just fillers to make people say "OMG that's so awesome!" and stuff like that.
I was wondering the same thing at first. The Inuyasha movies are made by different people completely. It's kinda weird. They aren't made in any specific order in relation to the episodes. The movies are just made for us crazy Inuyasha fans. The series isn't connected to the movies and the movies aren't cconnected to the series. That's just how it is.